Tutorial (Intermediate level): Coded Targets & Scale Bars in Agisoft PhotoScan Pro 1.1

This tutorial shows how coded targets can be used in PhotoScan Professional for coordinate system or scaledefinition. Also the main principles of scale bars usage are described.

OverviewCoded targets are printed markers that can be placed in the scene before photos are taken andcould be used in PhotoScan Professional as reference points for coordinate system and scaledefinition or as a valid matches between images to help camera alignment procedure via“Align Selected Cameras” option.

How to Print Coded Targets

Select Print Markers... command in the Tools → Markers menu:

The selected parameters will be used for PDF file generation in the Print Markers dialog.

Recommended settings for marker printing are the following:Marker type: 12 bitCenter point radius, mm: 10Targets per page , mm: 6

Click OK and in the opened Save As dialog specify the folder for PDF file to be saved in.

Exported PDF file will contain all the possible coded targets and it is not necessary to print allthe pages. Select few pages (depending on the number of targets to be placed) from themiddle of the document and send them to the printer.

How to Place Coded Targets in Scene and Take Photos

Coded targets should be flat, any deformations should be avoided.Coded targets should be circles with black and white segments, so you have to cut themkeeping in mind circle dimensions.Any changes in the coded target pattern must be avoided.

Once the coded targets are printed, place them in the scene or around the object of interest sothat they could be clearly seen from at least of couple or images.

Note that the size of the coded targets should not be too big or too small compared to theobject or scene. It is recommended that the size of central black circle-point on the takenphoto is not greater than 30 pix.

How to Detect Coded Targets AutomaticallySelect Detect Markers... command in the Tools menu:

In the Detect Markers dialog choose corresponding Marker Type and adjust Tolerance value.Click OK and wait until marker detection procedure is finished.

Tip: PhotoScan Pro supports automatic detection of 12-, 16- and 20- bit coded targets. Also Cross and Circle non-coded targets are supported (see examples below), but non-coded target detection is only possible after camera alignment is finished (see the examples of non-coded cross and circular targets below).Inverted flag can be used to detect white targets on the black background.Parity check is applicable for coded targets only and means that targets can have only even number of black sectors.

Detected markers will be named correspondingly to the coded targets labels.

How to Create Scale Bar and Set Up Reference Distance

Providing that before or after the shooting session some of the linear distances between thecoded targets have been measured, it is possible to set up the scale of the model using thisinformation.

Actually, coded targets detection could be performed even after the model has been processed.So in case the camera position have not been estimated yet, proceed to Align Photosprocedure.

Once the photos are aligned you can see the markers in the Model view:

To create a scale bar consequently left-click on the markers in the Model view (with anyselection tool active, while holding the Ctrl key), that correspond to the scale bar ends. Thenright-click in the model view or on the pair of selected markers in the Workspace pane to openthe context menu and select Create Scale Bar option. Repeat for every pair of markers withknow distance between them.

Go to the Reference pane and inset the distance for every scale bar the distance is known for:

Check all the scale bars you want to use for model scaling and press Update button.The scale will be applied to the model.

To apply correct model orientation in space use Rotate Object tool.